DESCRIPTION: This is a study to determine whether diabetic nephropathy (DN) is genetically linked to any of a set of proposed candidate gene whose function in the kidney suggests a role in genetic susceptibility, and to use microarray technology to identify genes that are differentially expressed in the kidneys of diabetics with and without DN. cDNAs for candidate genes, as well as random clones from a kidney cDNA library, will be screened. Previously identified candidate genes, and other known genes that were not considered candidates, will be identified by this test for differential expression. It is also possible that previously unknown genes will be identified in this way. All of these genes will be given high priority and extra scrutiny in these tests for linkage with DN. Using sequence information for each of these genes and nearby regions, polymorphisms in and near the genes will be identified. To test for linkage, the investigators are assembling a panel of families that have several members with DN, or are otherwise suitable for linkage analysis. Tests will be carried out for linkage disequilibrium (using the transmission/disequilibrium test, TDT) and where possible, affected sib pair and other sib pair test methods.